[utils] adding string_is_digit function, similar to Python\'s (i.e. counts if it's in the Nd unicode category)

src/string_utils.c

@@ -482,6 +482,32 @@ inline size_t utf8_common_prefix_ignore_separators(const char *str1, const char
     return utf8_common_prefix_len_ignore_separators(str1, str2, strlen(str2));
 }
 
+bool string_is_digit(char *str, size_t len) {
+    uint8_t *ptr = (uint8_t *)str;
+    size_t idx = 0;
+
+    bool ignorable = true;
+
+    while (idx < len) {
+        int32_t ch;
+        ssize_t char_len = utf8proc_iterate(ptr, len, &ch);
+
+        if (char_len <= 0) break;
+        if (ch == 0) break;
+        if (!(utf8proc_codepoint_valid(ch))) return false;
+
+        int cat = utf8proc_category(ch);
+        if (cat != UTF8PROC_CATEGORY_ND) {
+            return false;
+        }
+
+        ptr += char_len;
+        idx += char_len;
+    }
+
+    return true;
+}
+
 bool string_is_ignorable(char *str, size_t len) {
     uint8_t *ptr = (uint8_t *)str;
     size_t idx = 0;